Oil recovery process using polyalkene oxide polymer solutions with added cations

ABSTRACT

Oil is displaced from oil-bearing formations by injecting into the formations aqueous compositions which include polyalkene oxide polymers and controlled quantities of alkaline earth metal ions. Similar compositions can also be used as viscosity increasing ingredients in other applications.

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Norton et al. p [451 Sept. 19, 1972 1 OIL RECOVERY PROCESS USING [56] HReferences Cited POLYALKENE OXIDE POLYMER SOLUTIONQ WI CATIONS I UNITEDSTATES PATENTS [72] Inventors: Charles J. Norton, Denver, Colo. 21-1968"166/275 80218 David 0 Falk Denver 3,018,826 l/l962 Sandrford....l66/273 Colo- 80236 3,343,601 9/1967 Pye ..l66/275 [73] Assignee:Marathon Oil Company, Findlary, Primary Examiner-Staph? Novosad OhioAttorney-Joseph C. Herring, Richard C. W1llson, Jr.

and Jack L. l-lummel [22] Filed: Oct. 9, 1970 21 Appl. No.: 79,591 [57]ABSTRACT Oil is displaced from oil-bearing formations by injecting intothe formations aqueous compositions which [1.8- CI. R i lude polyalkeneoxide polymers and cgntroned CL ..EZlb quantities of alkaline earthmetal ions com- Field 0f Search positions can also be used as viscosityincreasing in- 252/8.55 D, 8.55 R i gredients in other applications.

8 Claims, 3 Drawing Figures 56 l I I l I POLYOX AND 606/; DISSOLVEOS/Ml/UANEOUSU (I O D 32 ll.

Z hl u 24 I 3 oz rox PREDISSOL v50 8 0 POLYOX (500 PPM) SOLUTION MADE UPTHEN ADDED TO CoCl I POLYOX (500 PPM) AND CoCl SIMULTANEOUSLY DISSOLVEDO l l 1 l r l PAIENTEDsEP I9 I972 sum 1 0F 5 GLASS BULBS TIMING MARKSSCREEN PACK SCREEN "VISCOMETER" POLYMER SOLUTION TIME SCREEN FACTORSOLVENT TIME Fig. I

W/T/VESSES.

CHARLES J. NORTON 2-; DAVID ov FALK ATTORNEY PATENTEU 3.692.113

SHEET 3 0F 3 I! O a h- Z ll-l I1] m O O 1 l I l I METAL ION, PPM

Fig. 3

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A TTOR/VE) OIL RECOVERY PROCESS USING POLYALKENE OXIDE POLYMER SOLUTIONSWITH ADDED CATIONS CROSS REFERENCES TO RELATED APPLICATIONS Thefollowing cases relate processes the same general field as that of thepresent invention: U.S. Pat.

BACKGROUND OFv THE INVENTION 1. Field of the Invention The presentinvention relates primarily to wells classified in class 166 of theUnited States Patent Office, and more particularly to a production ofearth fluid by driving fluid classified in class 166 subclass 252.

2. Description of the Prior Art Polyalkene oxides, e.g. polyethyleneoxides, are described in the Union Carbide Corporation bulletins ontheir polyethylene oxide, Polyox Registered trademark of the UnionCarbide Co.) e.g. their Bulletin f-40 246E, M1968 Mixedpolyethylenepolypropylene oxides are described in Wyandotte ChemicalCompany Bulletin f-30l8R. Factors influencing mobility control bypolymer solutions are discussed in Paper no. SPE 2867 of the Society ofPetroleum Engineers of the American Institute of Mining'Engineers, whichpaper also describes the screen viscometer and screenfactor discussedlater in this application.

However, none of the prior art, to the best of our knowledge, teachesthe increased flow resistance of polyalkene oxides in aqueous solutionin the presence of metal ions, as included within the present invention.

SUMMARY General Statement of the Invention Polyalkene oxide polymershave been used as thickening agents to increase the viscosity of liquidsincluding among others, displacing liquids for use in primary,secondary, and tertiary petroleum recovery. Such uses are taught, e.g.,in the American Institute of Mining Engineers paper Factors InfluencingMobility Control by Polymer Solution by R. R. Jennings, J. H. Rogers,and T. .1. West, SPE Paper No. 2867 prepared for the Ninth BiennialProduction Techniques Symposium, held in Wichita Falls, Texas, May14-15, 1970. Such polyalkene oxides decrease the mobility of thedisplacing liquids to improve their efficiency in displacingoil-in-place from formations and moving the oil toward production wells.Decreasing the mobility of the displacing fluids minimizes fingering orchannelling of the displacement fluids through the body of oil-in-placein the formation.

A laboratory method for obtaining a measure of the relative mobility offluids is described in the above paper by Jennings, ital.

FIG. 1 shows the general type of apparatus utilized in such testing. Inthe testing, the liquids flow through screens and the ratio of the timerequired for the test solution to flow through the screen viscometerdivided by the time required for a standard solvent water to flowthrough the viscometer is termed the screen factor.

According to the present invention, the factor, of aqueous solutions ofpolyethylene oxide can be inexpensively and effectively increased by theaddition of metal ions, preferably selected from the group consisting ofalkaline earth metal ions. The present invention is useful with any ofthe general class of polyalkene oxides including polyethylene oxide,polypropylene oxide, mixed copolymers of polyethylene oxide andpolypropylene oxide. The preferred polyalkene oxides have molecularweights of from aboutlO to about 10 more preferably from 10 to about10', and most preferably from 1.0 X 10 to about 6.0 X 10'.

As mentioned above, the processes and compositions of the presentinvention are useful for the decreasing of mobility of liquid solutionsespecially for use in the secondary and tertiary recovery of petroleumby displacement of oil-in-place from subterranean oil-bearingformations. In general, the techniques of secondary and tertiaryrecovery are applicable to the use of the invention and standard workssuch as Secondary Recovery by C.R.Smith, (Reinhold, 1966) should beconsulted in this connection.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of thescreen viscometer utilized in the determination of screen factor.

FIG. 2 is a plot of screen factor" versus Polyox" (500 ppm)concentration at various levels of parts per million of calcium ion. Thetwo curves represent values when Polyox is predissolved and when Polyoxand calcium chloride are dissolved simultaneously as described inExamples 1 to 4.

FIG. 3 is a plot of screen factor as a function of metal ionconcentration (ppm) for Ba, Mg, Ca and Zn, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Starting Materials As mentionedabove, the polyalkene oxides will preferably have molecular weights inthe range of from about 10 to about l0 more preferably from 10 to about10, and most preferably from 1.0 X 10 to about 6.0 X 10. Preferably, thepolyalkene oxides will be present in amounts of from 0.001 to about10.0, more preferably from 0.01 to about 1.0, and most preferably from0.05 to about 0.5 weight percent based on the weight of the totalsolution.

The alkaline earth metal cations used in the present invention can bederived from salts of the corresponding metals, e.g., chlorides,bromides, nitrates, sulfates, chlorate, acetates, and borates. Ingeneral, any salt which is soluble in the aqueous solutions so as toprovide sufficient concentration of the alkaline earth metal ions can beutilized with the invention. Typical examples include calcium salt, e.g.chloride, bromide, chlorate, nitrate, sulfate, and acetate.

While not narrowly critical, the amount of alkaline earth metal ion willgenerally be in the range of from 0.1 to about 300,000, more preferablyfrom to about 30,000, and most preferably from 100 to about 3,000 partsby weight of cation per million parts of solution.

The solvent for the liquid solutions of the present in vention willcomprise water, most preferably consist essentially of water. The waterused with the present invention may be connate water, e.g., weaklysaline Palestine line water, fresh water, or brackish water. It ispreferably that the water contain less than about 300,000, morepreferably less than about 10,000, and most preferably less than about100 parts per million of dissolved solids, exclusive of their alkalineearth content.

While not necessary to the practice of the present invention variousother ingredients including among others, cellulose and surfactants,e.g., polyalkylaryl sulfonates and other conventional displacement fluidadditives may be added to the liquid polymer solutions. In addition topolyalkene oxides, other viscosity increasing agents, e.g.,carboxymethyl cellulose, polyacrylamides, partially hydrolyzedpolyacrylamides, polyvinylpyrollidones, and polysaccharides may beemployed. Any of the afore-mentioned specific ingredients may beemployed in admixture.

Preparation of Liquid Solutions In general, it is necessary that thepolyalkylene oxide be dissolved either with or after the alkaline earthmetal salt. As shown in FIG. 2, when the Polyox or other polyalkeneoxide is dissolved and the salt thereafter added, virtually no increasein screen factor occurs. This difference in properties is the surprisingfeature of the invention. The ingredients may be readily dissolved intothe water by adding the polyalkene oxide and salt (or first dissolvingthe salt) while gently stirring to promote dispersion and dissolving.The ingredients will preferably be mixed with temperatures somewhatabove room temperature, more preferably from 0 C. to about 100 C., andmost preferably from to about 30 C. If desired, the mixing operation canbe accomplished in one or more flow-type mixers or mixing tees so longas the properties of ingredients are properly measured and thoroughlymixed.

EXAMPLES EXAMPLES I-lV In the examples that follow, to minimize sideeffects, solutions are prepared by dissolving the polyalkene oxidespecified in deionized water and simultaneously adding a sufficientquantity of the calcium chloride salt to provide the specifiedconcentration of the metal. The solution compositions and properties aresummarized in Table l which follows:

Polyox (500 ppm) 200 7.17 2.5 53.31 deionized water 300 6.97 3.4 57. 18added to dry Polyox and CaCl, tested after three days standing ll.856584-1112- 7.42 28.73 13 Repeat of 200 7.42 25.81 B56580-15-l6-17. 3007.00 36.81 Same solutions after standing five days and tested four times111. 856586-1-2-3- none 7.78 3.6 20.00 4-5 polyox (500 ppm) 100 ppm 7.673.5 18.78 Polyox solution 300 ppm 7.61 3.5 18.46 added to dry CaCl 500ppm 7.72 3.6 18.98 dissolved and tested 750 ppm 7.85 3.6 18.91 on sameday 1000 ppm 7.83 3.6 18.75 IV. 856587-1-2 100 ppm 7.32 3.7 46.89 Repeatof B56580- 300 ppm 7.65 3.8 53.05 15-17) New solutions.

Deionized water added to dry Polyox and CaCl,; Tested on same day[Polyox] [Conc.] V, B56590-5-6 100 6.94 2.1 16.78 [Ca**] (300 ppm) 3007.26 3.0 41.46 CaC 1, solution added to dry Polyox Tested after one daystanding Polyox Conc. Polyox Standards 100 2.0 8.2 250 2.5 15.2 500 3.526.2

The screening factor effect is maximal when the Polyox is dissolvedafter or simultaneously with the calcium ion and least when the calciumions are dissolved into predissolved Polyox. While the invention is notto be restricted to any hypothesized mechanism, apparently the alkalineearth ion forms a strong association complex with or between portions ofthe Polyox chains at the oxygen atoms.

EXAMPLE VI A solution was prepared by simultaneous solution with slowstirring of 500 ppm Polyox (Union Carbide coagulant grade), 400 ppmsodium chloride, and 55 ppm calcium chloride. This clear solution had aBrook'- field viscosity (at 6 rpm) of 318 and a screen factor of 42.9.

EXAMPLE Vll A 3 inch diameter, 4 ft long section of plastic encasedBerea sandstone with 1070.0 cc pore volume, 0.208 porosity, and 323/mdaverage permeability (pretreated by firing at 825 F) was saturated withtwo pore volume (PV) of Henry field water (water containing 11,500 ppmchloride, 6,500 ppm sodium, 276 ppm calcium, and 167 ppm magnesium). Thewet core was then saturated with Henry crude oil to an initial oilsaturation of 0.593 PV of initial water saturation of 0.407 PV, andsubsequently secondarily flooded with 2 PV Henry water to a residual oilsaturation of 0.358 PV and residual water saturation of 0.642 PV tosimulate a conventional secondary recovery.

This prepared core was then flooded with the thickened aqueous solutionprepared in Example V1, injected at from 20 to 40 cc/hour (frontalvelocity of 1.8-3.7 ft/day). The recovery data at various injected porevolume throughputs of this solution are tabulated below:

PV Total Addition Throughput Crude Recovery, PV

EXAMPLE VIII When the solution prepared according to Example VI isinjected into an injection well in an amount of approximately 0.1 porevolumes based on the total pore volume of the formation, oil-in-place isdisplaced away from the injection well and flows toward a productionwell from which it is produced. The oil cut is high indicating thatlittle or no fingering or breakthrough of the displacement fluid intothe production well exists.

Modifications It should be understood that the invention is capable of avariety of modifications and variations which will be made apparent tothose skilled in the art by a reading of the specification and which areto be included within the spirit of the claims appended hereto. Mixturesof various alkaline earth metal ion and polyalkene oxides can beemployed.

What is claimed is:

1. In a process for the displacement of oil from oilbearing formationscomprising injecting into said formations aqueous compositionscomprising from about 0.01 to about 1.0 weight percent of polyalkeneoxide polymers, the improvement comprising increasing the screen factorof said aqueous compositions by adding to said compositions controlledquantities of alkaline earth metal ions, said controlled quantitiesbeing in the range of from about to about 3,000 parts per million ofsaid composition.

2. Processes according to claim 1 wherein the polyalkene oxide polymerhas a molecular weight above 100,000 prior to the addition of saidalkaline earth metal ions.

3. Processes according to claim 1 wherein the polyalkene oxide polymeris present in a concentration of from about 0.001 to about 5 percent beweight based on the weight of the water.

4. Processes according to claim 1 wherein the polyalkene oxide has amolecular weight of from 1,000,000 to about 10,000,000 prior to theaddition of alkaline earth metal ions.

5. Processes according to claim 1 wherein said polyalkene oxide polymerhas a concentration of 0.01 to about 1 percent by weight based on theweight of the water.

6. Processes according to claim 1 wherein the total composition of saidalkaline earth metal ions is from about 10 to about 300,000 parts permillion by weight based on the weight of the water.

7. Processes according to claim 1 wherein the polyalkene oxide comprisesgroups containing the structure:

wherein R, R", R', and R"" may be the same or different and are eachselected from t he group consisting of hydrogen, alkyl, and containingrom one to 20 car-

2. Processes according to claim 1 wherein the polyalkene oxide polymerhas a molecular weight above 100,000 prior to the addition of saidalkaline earth metal ions.
 3. Processes according to claim 1 whErein thepolyalkene oxide polymer is present in a concentration of from about0.001 to about 5 percent be weight based on the weight of the water. 4.Processes according to claim 1 wherein the polyalkene oxide has amolecular weight of from 1,000,000 to about 10,000,000 prior to theaddition of alkaline earth metal ions.
 5. Processes according to claim 1wherein said polyalkene oxide polymer has a concentration of 0.01 toabout 1 percent by weight based on the weight of the water.
 6. Processesaccording to claim 1 wherein the total composition of said alkalineearth metal ions is from about 10 to about 300, 000 parts per million byweight based on the weight of the water.
 7. Processes according to claim1 wherein the polyalkene oxide comprises groups containing thestructure:
 8. The Processes of claim 10 wherein R'', R'''', R'''''', andR'''''''' each contain from 1 to 6 carbon atoms, the balance of thesubstituents being hydrogen.